This section introduces aspects that may help facilitate a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
Next generation optical access networks would benefit from sensitivity and capacity improvement in support of 5G technology to fulfil desired reduced latency and higher bit rates. The coherent detection of phase modulated signals, such as QAM or PSK optical signals modulated according to phase-shift keying (PSK), quadrature-phase-shift-keying (QPSK), and quadrature-amplitude-modulation (QAM) constellations, areis a promising approaches to improve sensitivity and information capacity.